Land-use
Bottleneck for Net Zero?
Tiny bit of housekeeping to begin. After a year and a half of keeping to a weekly cadence with these notes, the intensity of my main endeavours in advancing climate solutions has ratcheted up (a good thing). As such, I’ll be publishing more on a fortnightly basis, or whatever I can manage. Housekeeping over.
I’m picking up the thread here from the last post on Erthos - flat earth solar. Firstly, I had a great response from Rob West at Thunder Said Energy, who did some work on the efficacy of solar trackers. He found that the benefit is exaggerated at higher latitudes where the sun moves through a wider range during the day, suggesting that the advantage from a cost perspective of trackers will persist over the Erthos approach until we get further cost declines in solar modules.
I also got a couple of responses in relation to the last-use question. Erthos can use between half and a third as much land for the same power generation because, although the panels will get 20% less energy (clearly somewhat dependent on location), they can fit 2.5-3.5x as many panels per unit of land. But how does that land use compare with how it could be used for other vectors for decarbonisation, such as forestry? And how do competing uses of land impact the path to Net Zero more generally? This conversation from Catalyst offers a good introduction to some of the challenges that I elaborate on below.
Firstly, just to knock this question of solar vs forest on the head. Using land to build solar plants beats tree planting hands down when it comes to decarbonisation impact. Land requirements for a 1MW solar farm is something like 2.5 hectares and the average output of a 1MW solar farm per year is about 2000 MWh. The average carbon intensity of the grid currently in the US is about 400 kg / MWh. In Europe it ranges from the very low in France (50kg / MWh - hello, nuclear!) and Sweden (9kg - hello, nuclear and hydro!) to the very high in Poland (710kg) and Estonia (775kg). So the carbon abatement of 2.5 hectares of utility solar feeding into the grid would be 800 tonnes / year in the US and would vary wildly by country in the EU. That compares to 1-10 tonnes of carbon per hectare for forest. So it's not even close.
This exercise also reveals the achilles heel of bioenergy as a means of mass energy production or, when paired with CCS, of drawdown. Photosynthesis converts sunlight to useful energy with an efficiency of about 0.2% compared to solar’s efficiency of 15-20% (which is getting better all the time). There is a reason we stopped burning wood to power our economy! Biofuels then will probably be mostly restricted to agricultural waste streams for particular applications that require liquid fuels. There will be increased demand for said waste streams. (Lots more on that here.)
Land challenges for high wind and solar penetration: In aggregate there is enough land to build wind and solar to meet our energy needs (something like 5% in the contiguous US - a LOT, but feasible). Germany is currently trying to find 2% of land mass to allocate to wind (compared with 0.5% used today).
However, much of the available land and renewable resources is far away from where the energy demand is (think SW for solar, mid-West and west Texas for wind in the US). This requires a lot of transmission capacity to be added.
Even as the demand has grown, the amount of new transmission in the US has been falling, hindered by difficulty in permitting, i.e. NIMBYism. Perfect example is when Maine residents rejected the construction of a power line to take Canadian hydropower to Massachusetts. Re-using the below graph from a few weeks back because of its power to disconcert!
The difficulties of permitting for long distance transmission are obviously mitigated where there isn’t a consultative planning process or where cables can be put underwater. Hence why China has managed to established a transnational high-voltage direct-current grid (HVDC - the type of transmission with the lowest energy losses) and why some of the most ambitious projects are looking at subsea transmission from deserts to population centres (Xlinks from Morocco to the UK and the Australia-Asia PowerLinks project). It also hints on the long term potential for over-the-horizon floating wind.
One innovation around long-distance sub-sea HVDC cables in particular that I think is worth watching is SuperNode, a company in the Aker group, that is developing superconducting cables that are cooled below critical temperature and allow for transmission of greater amounts of energy with less material and transmission losses. (The trick is keeping the cables cooled below -200 degrees C in a cost-effective manner.)
Another area that I think is worth watching is innovations that improve the outlook for underground cables. They have their challenges, including generally causing more disruption to land where they are buried (although with lower visual impact), increased cost, more difficulties with maintenance. However, maybe with improved tunnelling technology, the benefits will outweigh the costs. There is a company EarthGrid that is working on a plasma drill (like Quaise Energy, but going sideways rather than straight down) expressly for this purpose. The Boring Company also has utility tunnels as one of their applications. I’d be very interested in any reader feedback if this is a silly idea or not.
Subsurface real estate: Whilst there is ample geological storage capacity for storing CO2, there will still be competition for the best sites that are co-located with renewable resources / supplies of CO2 and where permitting can be obtained. There is also already a land grab (or cavern-grab?) on for salt domes that can store large amounts of hydrogen.